Method for producing allulose crystals

ABSTRACT

Allulose crystals are efficiently produced from an allulose syrup using seed crystals.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application No.62/414,280, filed Oct. 28, 2016, the entire disclosure of which isincorporated herein by reference for all purposes.

FIELD OF THE INVENTION

The present invention relates to the production of crystals of allulosefrom syrups containing allulose.

DISCUSSION OF THE RELATED ART

Many food and beverage products contain nutritive sweeteners such assucrose (generally referred to as ‘sugar’ or ‘table sugar’), glucose,fructose, corn syrup, high fructose corn syrup and the like. Althoughdesirable in terms of taste and functional properties, excess intake ofnutritive sweeteners, such as sucrose, has long been associated with anincrease in diet-related health issues, such as obesity, heart disease,metabolic disorders and dental problems. This worrying trend has causedconsumers to become increasingly aware of the importance of adopting ahealthier lifestyle and reducing the level of nutritive sweeteners intheir diet.

In recent years, there has been a movement towards the development ofreplacements for nutritive sweeteners, with a particular focus on thedevelopment of low or zero-calorie sweeteners. One proposed alternativeto nutritive sweeteners is allulose (also known as D-psicose). Alluloseis known as a “rare sugar”, since it occurs in nature in only very smallamounts. It is about 70% as sweet as sucrose, but provides only around5% of the calories of sucrose (approximately 0.2 kcal/g). It maytherefore essentially be considered to be a ‘zero calorie’ sweetener.

In view of its scarcity in nature, production of allulose relies on theepimerization of readily available fructose. Ketose-3-epimerases caninterconvert fructose and allulose, and various ketose-3-epimerases areknown for carrying out this conversion. Such epimerization reactions aretypically conducted using an aqueous medium in which fructose isinitially dissolved, wherein the allulose-containing product obtained asa result of the epimerization is in the form of a solution of allulosein water. Further processing and purification of the reaction productmay be conducted in accordance in known procedures, whereby an allulosesyrup containing allulose in fairly high concentration and purity isproduced. Such allulose syrups are capable of being used in manyconsumable products, including foods and beverages, as substitutes forconventional “sugar” syrups such as glucose syrups, high fructose cornsyrups and the like.

For other applications, however, it would be desirable to utilizeallulose which is in “dry,” free-flowing, crystalline form, i.e., a formgenerally resembling that of table sugar. Although some attempts todevelop procedures for producing crystalline allulose have been reported(see, for example, U.S. Pat. No. 8,524,888 and WO 2016/064087), it isgenerally recognized that allulose is a saccharide which is challengingto crystallize in a controlled, efficient way such that crystals ofsuitable shape and size are reliably obtained in high yield. Therefore,improved crystallization methods for allulose are still of greatinterest.

SUMMARY OF THE INVENTION

Various aspects of the present invention may be summarized as follows:

Aspect 1: A method for producing allulose crystals, wherein the methodcomprises:

-   -   a) cooling and agitating a first admixture comprised of a first        portion of allulose syrup and allulose seed crystals and        initiating crystallization of allulose dissolved in the allulose        syrup, thereby forming a first massecuite comprising allulose        crystals and a first mother liquor containing residual dissolved        allulose, the cooling and agitating being continued until a        first preselected target yield of allulose crystals is achieved;    -   b) optionally, separating the first massecuite into a first        portion (which may be subjected to further processing steps,        such as separating the allulose crystals from the mother liquor        portion and washing and/or drying the separated allulose        crystals) and a second portion;    -   c) optionally, combining a second portion of allulose syrup with        the second portion of the first massecuite to form a second        admixture; and    -   d) optionally, cooling and agitating the second admixture and        initiating crystallization of allulose dissolved in the second        portion of allulose syrup, thereby forming a second massecuite        comprising allulose crystals and a second mother liquor        containing residual dissolved allulose, the cooling and        agitating being continued until a second preselected target        yield of allulose crystals is achieved.

In various embodiments of Aspect 1, at least steps a) and b) areperformed, at least steps a)-c) are performed, or at least steps a)-d)are performed.

Aspect 2: The method of Aspect 1, wherein the first admixture isobtained by combining the first portion of allulose syrup and dryallulose crystals.

Aspect 3: The method of Aspect 1, wherein the first admixture isobtained by combining with the first portion of allulose syrup and aheel comprised of allulose crystals and a mother liquor.

Aspect 4: The method of any of Aspects 1-3, wherein the first admixtureand second admixture are agitated in steps a) and d), if step d) isperformed, respectively using an agitator having a tip speed of 0.02 to2 m/sec.

Aspect 5: The method of any of Aspects 1-4, wherein step a) additionallycomprises, following initiation of crystallization of allulose dissolvedin the allulose syrup, combining at least one additional portion ofallulose syrup with the first admixture.

Aspect 6: The method of any of Aspects 1-5, wherein the cooling in stepa) involves lowering the temperature of the first admixture from withinan initial temperature range to within a second temperature range andholding the temperature of the first admixture within the secondtemperature range for a period of time.

Aspect 7: The method of any of Aspects 1-6, wherein step d) is performedand the cooling in step d) involves lowering the temperature of thesecond admixture from within an initial temperature range to within asecond temperature range and holding the temperature of the secondadmixture within the second temperature range for a period of time.

Aspect 8: The method of any of Aspects 1-7, wherein the allulose syruphas a dry solids content of 70% to 95% by weight, 75% to 90% by weight,or 80% to 85% by weight.

Aspect 9: The method of any of Aspects 1-8, wherein the allulose syruphas an allulose purity of at least 70%, at least 75%, at least 80%, atleast 85%, or at least 90%.

Aspect 10: The method of any of Aspects 1-9, comprising an additionalstep of separating allulose crystals from the first mother liquor in thefirst portion of the first massecuite.

Aspect 11: The method of Aspect 10, wherein the separating is carriedout at least in part by one or more physical separation methods selectedfrom the group consisting of centrifugation, filtration, decantation,membrane separation and combinations thereof.

Aspect 12: The method of Aspect 10 or 11, wherein allulose crystalsseparated from the first mother liquor are subjected to i) washing withat least one of water, an organic solvent, a blend of organic solvents,a blend of water and organic solvent(s) or an aqueous solution comprisedof at least one carbohydrate (e.g., allulose); ii) drying; or acombination thereof.

Aspect 13: The method of any of Aspects 1-12, wherein steps b)-d) areperformed and repeated at least once.

Aspect 14: A method for producing allulose crystals, wherein the methodcomprises:

-   -   a). passing a feed syrup/recycled massecuite admixture,        comprised of i) a feed syrup, comprising water and dissolved        allulose, and ii) a recycled massecuite comprising allulose        crystals and a recycled massecuite mother liquor containing        dissolved allulose, wherein the feed syrup/recycled massecuite        admixture has been cooled to within a first crystallization        temperature range, through a first stage crystallization zone,        while agitating the feed syrup/recycled massecuite admixture,        maintaining the feed syrup/recycled massecuite admixture within        the first crystallization temperature range and initiating        crystallization of allulose dissolved in the feed syrup and        recycled massecuite mother liquor, thereby forming a first        massecuite comprising allulose crystals and a first mother        liquor containing residual dissolved allulose, and withdrawing        the first massecuite which has achieved a first preselected        target yield from the first stage crystallization zone;    -   b). optionally, cooling the first massecuite withdrawn from the        first stage crystallization zone to within a second        crystallization temperature range and transferring the first        massecuite to a second stage crystallization zone;    -   c). optionally, passing the first massecuite through the second        stage crystallization zone while agitating the first massecuite,        maintaining the first massecuite within the second        crystallization temperature range and initiating crystallization        of allulose dissolved in the first mother liquor, thereby        forming a second massecuite comprising allulose crystals and a        second mother liquor containing residual dissolved allulose, and        withdrawing the second massecuite which has achieved a second        preselected target yield from the second stage crystallization        zone; and    -   d). optionally, repeating steps b and c at least once to yield a        final massecuite comprising allulose crystals and a final mother        liquor.

In various embodiments of Aspect 14, at least steps a) and b) areperformed, at least steps a)-c) are performed, or at least steps a)-d)are performed.

Aspect 15: The method of Aspect 14, wherein steps a)-d) are performedand comprising an additional step of separating the allulose crystals inat least a portion of the final massecuite from the final mother liquor.

Aspect 16: The method of Aspect 14 or 15, wherein steps a)-d) areperformed and a portion of the final massecuite is used as the recycledmassecuite.

Aspect 17: The method of any of Aspects 14-16, wherein the feedsyrup/recycled massecuite admixture is obtained by mixing in a mixingvessel the feed syrup with the recycled massecuite comprised of allulosecrystals and a recycled massecuite mother liquor containing dissolvedallulose to provide the feed syrup/recycled massecuite admixture andtransferring the feed syrup/recycled massecuite admixture from themixing vessel into the first stage crystallization zone.

Aspect 18: The method of any of Aspects 14-17, wherein the firstadmixture and second admixture are agitated in steps a) and c), if stepc) is performed, respectively using an agitator having a tip speed of0.02 to 2 m/sec.

Aspect 19: The method of any of Aspects 14-18, wherein the allulosesyrup has a dry solids content of 70% to 95% by weight, 75% to 90% byweight, or 80% to 85% by weight.

Aspect 20: The method of any of Aspects 14-19, wherein the allulosesyrup has an allulose purity of at least 70%, at least 75%, at least80%, at least 85%, or at least 90%.

Aspect 21: The method of Aspect 15, wherein the separating is carriedout at least in part by one or more physical separation methods selectedfrom the group consisting of centrifugation, filtration, decantation,membrane separation and combinations thereof.

Aspect 22: The method of Aspect 15 or 21, wherein allulose crystalsseparated from the final mother liquor are subjected to i) washing withat least one of water, an organic solvent, a blend of organic solvents,a blend of water and organic solvent(s) or an aqueous solution comprisedof at least one carbohydrate (e.g., allulose); ii) drying;

or a combination thereof.

Aspect 23: The method of any of Aspects 14-22, wherein the feedsyrup/recycled massecuite admixture is passed through the first stagecrystallization zone in a plug flow manner and/or, if steps b) and c)are performed, the first massecuite is passed through the second stagecrystallization zone in a plug flow manner.

Aspect 24: The method of any of Aspects 1-23, wherein the method isperformed in a continuous manner.

Aspect 25: Allulose crystals, obtained in accordance with the method ofany of Aspects 1-24.

Aspect 26: A consumable product, comprised of or prepared using allulosecrystals in accordance with Aspect 25 and at least one additionalingredient other than allulose crystals.

Aspect 27: A method of making a consumable product, comprising usingallulose crystals in accordance with Aspect 25.

Aspect 28: A mother liquor, obtained in accordance with the method ofany of Aspects 1-24.

Aspect 29: The mother liquor of Aspect 28, wherein the mother liquor issuitable for use as a product consumable by humans or animals or as aningredient in a formulated product consumable by humans or animals.

DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates in schematic form a crystallization system andprocess in accordance with one embodiment of the invention.

FIG. 2 is a microscopic image of a massecuite containing allulosecrystals which has been produced in accordance with an embodiment of theinvention.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE INVENTION AlluloseSyrup

The present invention utilizes at least one allulose syrup as a startingmaterial for a crystallization process, wherein allulose present indissolved form in the syrup is converted to crystalline form. Methods ofobtaining allulose syrups are well known in the art and are described,for example, in the following patent documents, the disclosure of eachof which is incorporated herein by reference in its entirety for allpurposes: WO 2016/135458; US 2015/0210996; U.S. Pat. Nos. 5,411,880;8,735,106; and 8,030,035.

For example, the allulose syrup may be prepared by a process comprisingcontacting an aqueous solution of fructose with an allulose (D-psicose)epimerase enzyme under conditions effective to convert at least aportion of the fructose to allulose, purifying the reaction productobtained, and then concentrating the purified reaction product to adesired dry solids content. The purification steps may involve theremoval of impurities from the reaction product using one or moretechniques such as deproteination, decolorization (treatment withdecolorizing agent(s)), desalting, ion exchange chromatography (usingone or more ion exchange resins, such as anion exchange resin, cationexchange resin and the like), column chromatography, fractionation, andthe like.

The allulose syrup should have a dry solids content which is sufficientto effect crystallization of allulose when the syrup is cooled in thepresence of seed crystals, as described hereafter in more detail. Forexample, in various embodiments, the dry solids content of the allulosesyrup may be at least 50% by weight, at least 55% by weight, at least60% by weight, at least 65% by weight, at least 70% by weight, at least75% by weight or at least 80% by weight. However, it will generally bepreferred that the dry solids content of the allulose be sufficientlylow that the syrup remains a free-flowing solution in the absence ofseed crystals at the temperature at which the syrup is to be maintainedprior to the initiation of crystallization by the introduction of seedcrystals. Thus, in various embodiments of the invention, the allulosesyrup has a dry solids content not greater than 90% or not greater than85%. The desired dry solids content may be attained by subjecting adiluted allulose solution to an evaporation or concentration procedurewherein volatiles (e.g., water) are removed from the solution, leavingbehind a more concentrated syrup. The evaporation/condensationconditions may advantageously be selected so as to minimize or reducethe extent of allulose degradation; for example, relatively lowevaporation temperatures may be employed.

The purity of the allulose syrup may vary, but typically it will bedesirable for allulose to constitute the majority, by weight, of thenon-volatile substances present in the allulose syrup. Accordingly, theallulose purity of the syrup may be, in various embodiments of theinvention, at least 60% by weight, at least 65% by weight, at least 70%by weight, at least 75% by weight, at least 80% by weight, at least 85%by weight or at least 90% by weight. The term “allulose purity” as usedherein with respect to an allulose syrup means the percent by weight ofallulose in the syrup, based on the total weight of dry solids in thesyrup.

Seed Crystals of Allulose

The present invention employs seed crystals of allulose to help promotethe initiation of crystallization of additional allulose from solution(e.g., the formation of solid crystals containing allulose that hadpreviously been in solution in an allulose syrup, mother liquor or thelike). In certain embodiments, the allulose seed crystals are in dryform (for example, dry crystals of allulose recovered from a previouslyperformed crystallization) and/or in the form of a heel, such as aportion of a massecuite comprised of allulose crystals and a motherliquor. The precise amount of allulose seed crystals is not believed tobe particularly critical, but may, for example, be employed in aquantity representing from about 0.1 to about 5% of the total amount ofallulose present in a crystallization vessel or crystallization zone, aswill be described in more detail subsequently. Generally speaking,allulose seed crystals of relatively high purity are preferred for use;for example, the allulose seed crystals may have an allulose purity ofat least 90%, at least 95% or at least 99% by weight, in variousembodiments of the invention. The term “allulose purity” as used hereinwith respect to allulose crystals means the percent by weight ofallulose in the crystals, based on the total weight of dry solids in thecrystals.

Description of Various Exemplary Embodiments of Crystallization Process

In one embodiment of the invention, batch crystallization of allulosemay be performed in a jacketed vessel equipped with an agitator bydropping the temperature of the cooling medium (e.g., water or otherheat transfer liquid) in the jacket to lower the massecuite temperatureand thereby drive crystallization. The following series of steps may beperformed:

-   -   1. The vessel is partially filled with a suitable allulose        syrup.    -   2. The temperature of the cooling medium is set at a desired        initial temperature.    -   3. The agitator is started and set at an RPM effective to        provide a desired tip speed.    -   4. The temperature of the allulose syrup in the vessel is        lowered to a desired temperature, by varying the temperature of        the cooling medium as appropriate.    -   5. A desired amount of seed crystals (e.g., dry seed crystals)        is added to the vessel (this addition may be performed prior to        the time the allulose syrup reaches the temperature referenced        in step 2).    -   6. Mix the seed crystals and the allulose syrup, using an        appropriate agitator tip speed. The agitator tip speed may be        selected to minimize or avoid breakage of the seed crystals as        well as the allulose crystals subsequently formed during        crystallization. In certain embodiments, the agitator tip speed        is higher during the initial mixing of the seed crystals with        the allulose syrup than it is during the subsequent        crystallization step(s).    -   7. The temperature of the allulose syrup/seed crystal admixture        is then lowered to a desired temperature effective to achieve        crystallization of a portion of the allulose dissolved in the        allulose syrup. This temperature will vary, depending upon, for        example, the concentration of allulose in the syrup, but        typically will be not greater than about 40° C. and not less        than about 0° C.    -   8. Crystallization is permitted to continue, with a suitable        degree of agitation, until a desired yield of allulose crystals        is achieved (this may be checked by periodically withdrawing a        sample from the vessel and measuring the dry solids content of        the mother liquor).    -   9. To achieve the desired yield of allulose crystals, the        temperature of the massecuite may continue to be lowered, either        continuously or in one or more stages.    -   10. Once the desired yield of allulose crystals is met, the        massecuite is combined with an additional portion of allulose        syrup (filling the vessel, for example). Steps 7-9 are then        repeated.    -   11. Once the desired yield of allulose crystals is achieved        following the introduction of the additional portion of allulose        syrup into the vessel, a portion (e.g., approximately        one-quarter to three-quarters) of the massecuite is removed from        the vessel, with the remaining portion of the massecuite being        retained in the vessel to serve as a source of seed crystals for        a subsequent batch of massecuite. In this way, multiple batches        of massecuite may be prepared.    -   12. The portion(s) of the massecuite withdrawn from the vessel        may be subjected to one or more desired processing steps, such        as separating the allulose crystals from the mother liquor by        one or more physical separation methods selected from the group        consisting of centrifugation, filtration, decantation, membrane        separation and combinations thereof and then washing and/or        drying the separated allulose crystals.

In another embodiment of the invention, the crystallization may beconducted in a continuous manner involving a plurality of stages (e.g.,three or four stages). Such a process may be carried out using a systemas illustrated in schematic form in FIG. 1 and as further explained asfollows.

An allulose syrup of suitable purity is introduced through line 1 toevaporator 2, wherein the dry solids content of the syrup is increasedto the desired level. The allulose syrup is then pumped (utilizing pump3) through line 4 into allulose syrup feed hold-up tank 5. From tank 5,the allulose syrup is pumped (using pump 6) via line 7 and introducedinto heat exchanger 8, wherein the temperature of the allulose syrup isadjusted to a desired value prior to being fed via line 9 to mix tank10. In mix tank 10, the allulose syrup is combined, using vigorousmixing, with massecuite from crystallization zone 22, which is fed tomix tank 10 using line 25. An admixture of allulose syrup and massecuite(which serves as a source of seed crystals) is withdrawn from mix tank10 and introduced into crystallization zone 12. Crystallization zone 12may be within a suitable tank or other vessel equipped with an agitator.Any agitator of the type known in the art may be used; in particular,the agitator may be any of the types of mechanical devices recognized asbeing useful in agitating solution/seed crystal mixtures in acrystallization process may be utilized. In one embodiment, the agitatorin the crystallization zone can bring about its agitating effecthorizontally but not vertically. In order to prevent or reduce turbulentflow and destruction/breakage of the crystals formed duringcrystallization, the agitation can be preferably carried out at a lowspeed. The agitator may be configured and operated so as to preventcrystals of allulose from adhering to the wall(s) and/or the bottom of avessel constituting crystallization zone 12. According to one aspect ofthe invention, the admixture of allulose syrup and massecuite is notsubjected to concentration within crystallization zone 12. The allulosesyrup/massecuite admixture may move through crystallization zone 12 in aplug flow manner, with the tip speed of the agitator being adjusted asappropriate to promote crystallization of allulose dissolved in theliquid phase of the admixture and to generate allulose crystals of thedesired size and shape. In one embodiment, the process parameters arecontrolled such that the allulose syrup/massecuite admixture is passed,in a descending continuous flow, through a vessel comprisingcrystallization zone 12. The flow rate of the admixture throughcrystallization zone 12 and thus the residence time of the admixture incrystallization zone 12 are controlled such that the admixture exitingfrom crystallization zone 12 via line 14 has a desired content ofallulose crystals (i.e., the desired yield of allulose crystals isachieved by the time the admixture is withdrawn from crystallizationzone 12). In one embodiment, the temperature of the allulosesyrup/massecuite admixture remains constant or essentially constant asthe admixture passes through crystallization zone 12. For example, thetemperature of the admixture may be controlled such that the admixturetemperature at the point of introduction into crystallization zone 12differs by no more than 5° C., no more than 4° C., no more than 3° C.,no more than 2° C. or no more than 1° C. from the temperature of theadmixture at the point where it exits or is withdrawn fromcrystallization zone 12.

The massecuite obtained from crystallization zone 12 is further cooledusing heat exchanger 15 to a desired temperature (which may be, forexample, about 1° C. to about 10° C. lower than the temperature of themassecuite as it exits from crystallization zone 12) and introduced intocrystallization zone 17, via line 16. According to one embodiment of theinvention, the massecuite obtained from crystallization zone 12 is notsubjected to concentration before or after being introduced intocrystallization zone 17. Crystallization zone 17 may be within asuitable tank or other vessel equipped with an agitator. The massecuitemay move through crystallization zone 17 in a plug flow manner, with thetip speed of the agitator being adjusted as appropriate to promotecrystallization of allulose still dissolved in the liquid phase (motherliquor) of the massecuite. The flow rate of the massecuite throughcrystallization zone 17 and thus the residence time of the admixture incrystallization zone 17 are controlled such that the admixture exitingfrom crystallization zone 17 via line 18 has a desired content ofallulose crystals (i.e., the desired yield of allulose crystals isachieved by the time the massecuite is withdrawn from crystallizationzone 17), with the desired content of allulose crystals being higherthan that of the massecuite withdrawn from crystallization zone 12. Themassecuite in crystallization zone 17 is not subjected to concentration,according to one embodiment of the invention.

The massecuite obtained from crystallization zone 17 is further cooledusing heat exchanger 20 to a desired temperature (which may be, forexample, about 1° C. to about 10° C. lower than the temperature of themassecuite as it exits from crystallization zone 17) and introduced intocrystallization zone 22, via line 21. According to one embodiment of theinvention, the massecuite obtained from crystallization zone 17 is notsubjected to concentration before or after being introduced intocrystallization zone 22. Crystallization zone 22 may be within asuitable tank or other vessel equipped with an agitator. The massecuitemay move through crystallization zone 22 in a plug flow manner, with thetip speed of the agitator being adjusted as appropriate to promotecrystallization of allulose still dissolved in the liquid phase (motherliquor) of the massecuite. The flow rate of the massecuite throughcrystallization zone 22 and thus the residence time of the admixture incrystallization zone 22 are controlled such that the admixture exitingfrom crystallization zone 22 via line 23 has a desired content ofallulose crystals (i.e., the desired yield of allulose crystals isachieved by the time the massecuite is withdrawn from crystallizationzone 22), with the desired content of allulose crystals being higherthan that of the massecuite withdrawn from crystallization zone 17. Themassecuite in crystallization zone 22 is not subjected to concentration,according to one embodiment of the invention.

If so desired, one or more additional crystallization zones (notillustrated) may be introduced, which is or are operated in a mannersimilar to that of crystallization zones 12, 17 and 22, wherein themassecuite exiting crystallization zone 22 is subjected to furthercooling and crystallization. According to certain embodiments of theinvention, such further processing is carried out without anyconcentration of the massecuite.

Once a massecuite having the desired final target yield of allulosecrystals has been produced, a portion of it may be recycled and utilizedas a source of seed crystals as previously mentioned (being conveyed vialine 25 to mix tank 10) and the remaining portion may be passed throughheat exchanger 27 and fed via line 28 to massecuite hold-up tank 29. Themassecuite from massecuite hold-up tank 29 may be subjected to aseparation of the allulose crystals from the mother liquor usingcentrifuge 30, with the resulting cake of allulose crystals then beingwashed before being dried in rotary dryer 31.

Generally speaking, it will be desirable to control the crystallizationconditions such that the final massecuite (i.e., the massecuite fromwhich allulose crystals will be recovered, involving separation from themother liquor component of the massecuite) does not have an overly highcontent of allulose crystals, since a high allulose crystalconcentration may tend to result in a massecuite which has a highviscosity and which is consequently difficult to further process.Accordingly, in various embodiments of the invention, the yield ofallulose crystals in the final massecuite is not more than 60%, not morethan 55%, not more than 50% or not more than 45%. At the same time, itis desirable for the allulose crystal yield which is achieved in thefinal massecuite to be sufficiently high so as to reduce productioncosts. Thus, in various embodiments, the yield of allulose crystals inthe final massecuite is at least 20%, at least 25%, at least 30%, atleast 35% or at least 40%.

The mother liquor(s) separated from allulose crystals in accordance withvarious embodiments of the invention may be further processed and/orused in different ways. For example, a mother liquor recovered from aseparation step may be simply used as is (e.g., in solution or syrupform) as a source of allulose in preparing or formulating a consumableproduct. If so desired, the mother liquor may be subjected to one ormore processing steps such as concentration (evaporation) and/ortreatment to remove impurities (using adsorbents or the like). In stillother embodiments, a recovered mother liquor may be recycled back into acrystallization process of the type described herein, thus serving as asource (in whole or in part) of an allulose syrup starting material.Prior to such recycling, the mother liquor may be subjected to one ormore processing steps such as concentration and/or purification.

Further Processing of Allulose Crystals

In various embodiments of the present invention, the method may compriseone or more additional steps wherein the allulose crystals present in amassecuite, following separation from the mother liquor portion of themassecuite by centrifugation, filtration, decantation, membraneseparation or other such physical separation method, are subjected tofurther processing. For example, allulose crystals as separated from amother liquor typically have some amount of the mother liquor on theouter surface to the crystals. Because the mother liquor generallycontains some amount of impurities (substances other than allulose), thepurity of the recovered crystals may be improved by subjecting theseparated allulose crystals to one or more washing steps, wherein one ormore volumes of a suitable liquid are used to wash the crystals. Thewashing step(s) may be performed in any suitable manner using techniquesknown in the art, such as passing the washing liquid through a bed ofthe allulose crystals or by slurrying the separated allulose crystals ina volume of the washing liquid and then subjecting the slurry to aphysical separation step such as centrifugation, decantation, membraneseparation and/or filtration to recover washed allulose crystals fromthe washing liquid. Any suitable washing liquid may be utilized, such aswater, an organic solvent (e.g., an alcohol, such as ethanol), a blendof water and one or more organic solvents, a blend of two or moreorganic solvents, and/or an aqueous solution comprised of at least onecarbohydrate such as allulose. In one embodiment, the allulose crystalsare washed with an allulose syrup or even a recovered mother liquorhaving a purity (with respect to allulose) that is higher than thepurity of the residual mother liquor initially present in the crystalsto be washed.

The allulose crystals separated from the mother liquor of a massecuitemay be subjected to a drying step to lower the moisture content of thecrystals. The drying step may, for example, be carried out subsequent toa washing step or series of washing steps. The drying of the crystalsmay be performed in a fluidized bed dryer, a rotary dryer, a vacuumdryer or other such apparatus. For example, in the drying step, theallulose crystals may be dried using an air temperature of up toapproximately 100° C., preferably no greater than 80° C., over a periodof about 20 minutes to about 24 hours, more preferably about 20 minutesto about 6 hours.

The present invention is capable of producing dry, relatively large,free-flowing crystals of allulose at a lower manufacturing cost (due tobetter utilization of equipment), as compared to previously knownallulose crystallization processes. Such larger crystals have a betterappearance than small allulose crystals, which often appear powdery orfluffy. Larger crystals have fewer fines, which in turn leads to lowerdusting. Fines (i.e., small crystals) can pack into the spaces betweenlarge crystals, possibly resulting in poor flow characteristics as wellas caking issues. Additionally, small crystals of allulose have greatersurface area as compared to large crystals; this leads to fastermoisture sorption, which can also contribute to caking. Dry,free-flowing allulose crystals of the type which can be producedeconomically using the present invention permit handling by a customer(e.g., a food manufacturer) without the need for special handlingequipment.

Processes in accordance with the present invention are capable, forexample, of producing an allulose crystal product having an averageparticle size of at least 100 microns, at least 150 microns, at least200 microns, or at least 250 microns or even larger (e.g., 250 to 350microns), in various embodiments of the invention. Average particle sizemay be determined using a laser diffraction particle size analyzer, suchas the LS 13 320 model manufactured by Beckman Coulter. According tocertain aspects of the invention, less than 25% of the allulose crystalproduct obtained is smaller than 75 microns in size.

The present invention can be practiced to obtain allulose crystalshaving a preferred morphology wherein the allulose crystal has awell-defined three-dimensional shape, rather than the shape of a needleor a flat sheet. FIG. 2 is a microphotographic image of allulosecrystals in a massecuite which have such a preferred morphology.

Allulose crystals produced in accordance with at least certainembodiments of the invention may advantageously have, for example, abulk density greater than 30 lb/ft³ and more preferably greater than 35lb/ft³.

Uses for Allulose Crystals

Allulose crystals produced by the method of the present invention may beused in a product for human and/or animal consumption. Such use isparticularly advantageous in products having a low water content. Insome embodiments, the product may be a food product, a beverage product,a pharmaceutical product, a nutritional product, a sports product, or acosmetic product. For example, when the product is a food product, thefood product can be selected from the group consisting of aconfectionary product (including a chocolate product), a dessertproduct, a cereal product, baked goods, frozen dairy products (e.g., icecream), meats, dairy products (e.g., yogurt), condiments, snack bars,energy bars, nutrition bars, soups, dressings, mixes, prepared foods,baby foods, diet preparations, syrups, food coatings, dried fruit,sauces, gravies, and jams/jellies. In some embodiments, the food productmay comprise allulose crystals produced by the method of the presentinvention in the form of a coating or frosting formed on the surface ofthe product. Alternatively, when the product is a beverage product, thebeverage product can be selected from the group consisting of acarbonated beverage, a non-carbonated beverage, fruit-flavored beverage,fruit juice, tea, milk, coffee, and the like. The food productcontaining allulose crystals produced in accordance with the inventionmay also be a tabletop sweetener.

Allulose crystals produced in accordance with the present invention maybe used in combination with one or more other food or beverageingredients, including any of the food and beverage ingredients known inthe art. Such additional food and beverage ingredients include, but arenot limited to, flavorants, colorants, sweeteners other than allulose(including other carbohydrates such as sucrose, fructose, allose,tagatose and other rare carbohydrates, synthetic high potency sweetenerssuch as sucralose, acesulfame K, saccharin, aspartame and the like,natural high potency sweeteners such as stevia and monk fruit extractsweeteners and the terpene glycosides present therein, such as steviolglycosides and mogrosides including, but not limited to, rebaudioside A,rebaudioside B, rebaudioside C, rebaudioside D, rebaudioside E,rebaudioside F, rebaudioside G, rebaudioside H, rebaudioside I,rebaudioside J, rebaudioside K, rebaudioside L, rebaudioside M (alsoknown as rebaudioside X), rebaudioside N, rebaudioside O, stevioside,steviolmonoside, steviolbioside, dulcoside A, dulcoside B, rubusoside,glycosylated steviol glycosides, enzyme-modified steviol glycosides,mogroside II A, mogroside II B, 7-oxomogroside II E, 11-oxomogroside A,mogroside III A₂, 11-deoxymogroside III, 11-oxymogroside IV A,7-oxomogroside V, 11-oxomogroside V, mogroside V, mogroside VI and thelike and combinations thereof), dietary fibers (including solubledietary fibers such as soluble corn fiber and polydextrose), acidulants,water, and the like. The allulose crystals may be admixed or blendedwith such other ingredients in dry form. In other embodiments, theallulose crystals may be coated with one or more other ingredients; forexample, a solution containing one or more other ingredients (such as ahigh potency sweetener, combination of high potency sweeteners, and/orone or more other carbohydrates), may be applied to the allulosecrystals by spraying or other such procedure and then dried.

1. A method for producing allulose crystals, wherein the methodcomprises: a) cooling and agitating a first admixture comprised of afirst portion of allulose syrup and allulose seed crystals andinitiating crystallization of allulose dissolved in the allulose syrup,thereby forming a first massecuite comprising allulose crystals and afirst mother liquor containing residual dissolved allulose, the coolingand agitating being continued until a first preselected target yield ofallulose crystals is achieved; b) optionally, separating the firstmassecuite into a first portion and a second portion; c) optionally,combining a second portion of allulose syrup with the second portion ofthe first massecuite to form a second admixture; and d) optionally,cooling and agitating the second admixture and initiatingcrystallization of allulose dissolved in the second portion of allulosesyrup, thereby forming a second massecuite comprising allulose crystalsand a second mother liquor containing residual dissolved allulose, thecooling and agitating being continued until a second preselected targetyield of allulose crystals is achieved.
 2. The method of claim 1,wherein at least steps a) and b) are performed.
 3. The method of claim1, wherein at least steps a), b) and c) are performed.
 4. The method ofclaim 1, wherein at least steps a), b), c) and d) are performed.
 5. Themethod of claim 1, wherein the first admixture is obtained by combiningthe first portion of allulose syrup and dry allulose crystals.
 6. Themethod of claim 1, wherein the first admixture is obtained by combiningwith the first portion of allulose syrup and a heel comprised ofallulose crystals and a mother liquor.
 7. The method of claim 1, whereinthe first admixture and second admixture are agitated in steps a) andd), if step d) is performed, respectively using an agitator having a tipspeed of 0.02 to 2 m/sec.
 8. The method of claim 1, wherein step a)additionally comprises, following initiation of crystallization ofallulose dissolved in the allulose syrup, combining at least oneadditional portion of allulose syrup with the first admixture.
 9. Themethod of claim 1, wherein the cooling in step a) involves lowering thetemperature of the first admixture from within an initial temperaturerange to within a second temperature range and holding the temperatureof the first admixture within the second temperature range for a periodof time.
 10. The method of claim 1, wherein steps a)-d) are performedand the cooling in step d) involves lowering the temperature of thesecond admixture from within an initial temperature range to within asecond temperature range and holding the temperature of the secondadmixture within the second temperature range for a period of time. 11.The method of claim 1, wherein the allulose syrup has a dry solidscontent of 70% to 95% by weight.
 12. The method of claim 1, wherein theallulose syrup has an allulose purity of at least 70%.
 13. The method ofclaim 1, comprising an additional step of separating allulose crystalsfrom the first mother liquor in the first portion of the firstmassecuite.
 14. The method of claim 13, wherein the separating iscarried out at least in part by one or more physical separation methodsselected from the group consisting of centrifugation, filtration,decantation, membrane separation and combinations thereof.
 15. Themethod of claim 13, wherein allulose crystals separated from the firstmother liquor are subjected to i) washing with at least one of water, anorganic solvent, a blend of organic solvents, a blend of water andorganic solvent(s) or an aqueous solution comprised of at least onecarbohydrate; ii) drying; or a combination thereof.
 16. The method ofclaim 1, wherein steps b)-d) are performed and are repeated at leastonce.
 17. A method for producing allulose crystals, wherein the methodcomprises: a). passing a feed syrup/recycled massecuite admixture,comprised of i) a feed syrup, comprising water and dissolved allulose,and ii) a recycled massecuite comprising allulose crystals and arecycled massecuite mother liquor containing dissolved allulose, whereinthe feed syrup/recycled massecuite admixture has been cooled to within afirst crystallization temperature range, through a first stagecrystallization zone, while agitating the feed syrup/recycled massecuiteadmixture, maintaining the feed syrup/recycled massecuite admixturewithin the first crystallization temperature range and initiatingcrystallization of allulose dissolved in the feed syrup and recycledmassecuite mother liquor, thereby forming a first massecuite comprisingallulose crystals and a first mother liquor containing residualdissolved allulose, and withdrawing the first massecuite which hasachieved a first preselected target yield from the first stagecrystallization zone; b). optionally, cooling the first massecuitewithdrawn from the first stage crystallization zone to within a secondcrystallization temperature range and transferring the first massecuiteto a second stage crystallization zone; c). optionally, passing thefirst massecuite through the second stage crystallization zone whileagitating the first massecuite, maintaining the first massecuite withinthe second crystallization temperature range and initiatingcrystallization of allulose dissolved in the first mother liquor,thereby forming a second massecuite comprising allulose crystals and asecond mother liquor containing residual dissolved allulose, andwithdrawing the second massecuite which has achieved a secondpreselected target yield from the second stage crystallization zone; andd). optionally, repeating steps b and c at least once to yield a finalmassecuite comprising allulose crystals and a final mother liquor. 18.The method of claim 17, wherein at least steps a) and b) are performed.19. The method of claim 17, wherein at least steps a), b) and c) areperformed.
 20. The method of claim 17, wherein at least steps a), b), c)and d) are performed.
 21. The method of claim 17, wherein steps a)-d)are performed and comprising an additional step of separating theallulose crystals in at least a portion of the final massecuite from thefinal mother liquor.
 22. The method of claim 17, wherein steps a)-d) areperformed and wherein a portion of the final massecuite is used as therecycled massecuite.
 23. The method of claim 17, wherein the feedsyrup/recycled massecuite admixture is obtained by mixing in a mixingvessel the feed syrup with the recycled massecuite comprised of allulosecrystals and a recycled massecuite mother liquor containing dissolvedallulose to provide the feed syrup/recycled massecuite admixture andtransferring the feed syrup/recycled massecuite admixture from themixing vessel into the first stage crystallization zone.
 24. The methodof claim 17, wherein at least steps a)-c) are performed and the firstadmixture and second admixture are agitated in steps a) and c)respectively using an agitator having a tip speed of 0.02 to 2 m/sec.25. The method of claim 17, wherein the allulose syrup has a dry solidscontent of 70% to 95% by weight.
 26. The method of claim 17, wherein theallulose syrup has an allulose purity of at least 70%.
 27. The method ofclaim 21, wherein the separating is carried out at least in part by oneor more physical separation methods selected from the group consistingof centrifugation, filtration, decantation, membrane separation andcombinations thereof.
 28. The method of claim 21, wherein allulosecrystals separated from the final mother liquor are subjected to i)washing with at least one of water, an organic solvent, a blend oforganic solvents, a blend of water and organic solvent(s) or an aqueoussolution comprised of at least one carbohydrate; ii) drying; or acombination thereof.
 29. The method of claim 17, wherein the feedsyrup/recycled massecuite admixture is passed through the first stagecrystallization zone in a plug flow manner and/or, if steps b) and c)are performed, the first massecuite is passed through the second stagecrystallization zone in a plug flow manner.
 30. The method of claim 1,wherein the method is performed in a continuous manner.
 31. Allulosecrystals, obtained in accordance with the method of claim
 1. 32. Aconsumable product, comprised of or prepared using allulose crystals inaccordance with claim 31 and at least one additional ingredient otherthan allulose crystals.
 33. A method of making a consumable product,comprising using allulose crystals in accordance with claim
 31. 34. Amother liquor, obtained in accordance with the method of claim
 1. 35.The mother liquor of claim 34, wherein the mother liquor is suitable foruse as a product consumable by humans or animals or as an ingredient ina formulated product consumable by humans or animals.